Good point. I never contemplated the possibility of going back. I was afraid of damaging the movement.You never have to move it 30 days. The date change works forwards and backwards -- going from 1 to 31 is 1 day, not 30, and so on. You can also change the date anytime you want, there is no "danger period" as there is with some movements.
I think 1/2 the people in this thread are talking about how to change the date manually, and the other half (and the OP) are talking about when the date changes itself in normal operation.